With the development of the future service, next generation wireless communication systems, such as 3GPP (third Generation Partnership Project) LTE (long term evolution) and beyond system, IMT-A (International Mobile Telecommunications-Advanced) system etc are introduced to satisfy high speed, large capacity, and a high QoS (Quality of Service) for billions of subscribers. A radio local area network for heterogeneous network architecture is deployed by the next generation wireless communication systems, to provide large capacity with an offload of the core network. For example, a technology of LTE-LAN (Long Term Evolution-Local Area Network)/LTE-Hi (LTE evolution for Hotspot and Indoor) is proposed to enhance the LTE local area. This kind of radio local area network may be connected to the core network through a radio access network of an associated base station (such as an eNB). In this instance, there's no direct interface between the radio local area network and the core network. When a user equipment (such as a mobile station) is working under such radio local area network, it can access local communication services supported by an access point (AP) of the radio local area network, without involving the radio access network and the core network (which can be collectively called as Evolved Packet System (EPS) network). Furthermore, the user equipment can also access EPS services supported by the associated base station, via the access point. Details of this kind of heterogeneous network architecture will be introduced later with reference to FIG. 1.